Limitations to photosynthesis in coffee leaves from different canopy positions.

摘要: Limitations to photosynthesis were explored in leaves from four canopy positions of field-grown, unshaded coffee (Coffea arabica L.), a tropical tree species classified as shade-obligatory. Overall, compared shade (lower) leaves, sun (upper) had higher net carbon assimilation rate (A) (4.5 against 2.0 micromol m(-2)s(-1) at most) associated with electron transport (due greater irradiance availability) but unrelated stomatal and mesophyll conductances, which similar regardless leaf position. Neither physiological variable directly involved photosynthetic gain nor those light capture able adjust themselves match the capacity machinery supply. We concluded that: (i) there was no major difference between leaves; (ii) intrinsic low A greatly remarkable diffusive limitations rather than biochemical or photochemical constraints; (iii) morphological (e.g., variations specific area inclination) anatomical plasticity should be acclimative value mean respond changing irradiance.